Ab Initio Effective One-Electron Potential Operators. II. Applications for Exchange-Repulsion Energy in Effective Fragment Potentials

In Paper I, the effective one-electron potentials (OEP) method was introduced and demonstrated as an efficient approach to reduce the computational cost of evaluation of the charge-transfer interaction energy within the effective fragment potential method (EFP2) by an average factor of 20, making it no longer a bottleneck in EFP2-based simulations of complex systems. Here, the OEP technique is used to enhance computational efficiency in evaluating the exchange-repulsion EFP2 interaction energy by redefining the first-order repulsive term of Murrell et al. [Murrell et al., Proc. R. Soc. Lond. A 284, 566 (1965)] through the extended density fitting in incomplete auxiliary basis. In the proposed approach the evaluation of the kinetic energy integrals is no longer required and the computational cost can be reduced roughly by a factor of 1.5 as compared to the original EFP2 formulation.